This invention relates to a composition for imparting anti-slip properties to the surface of a paper product.
During the manufacture of paper bags and boxes the surface of the paper is typically treated with a frictionizing agent to enhance the anti-slip properties of the surface of the finished product. The frictionizing agent increases resistance to slip and thus makes stacks of the finished bags or boxes more stable.
Compositions of colloidal silica are used as frictionizing agents in the paper industry to impart anti-slip properties to cellulose-based paper and fabricated wood products. The compositions are typically applied to a moving web using spray equipment or contact application equipment such as transfer rollers or sponges. Such methods tend to deposit the composition not only on the paper or wood surface as intended, but also as a residue in the immediate work area and on the application equipment. Conventional colloidal silica anti-slip compositions dry to a hard cementitious residue which cannot be redispersed in water. The cementitious residue thus tends to build up on the work area and equipment surfaces, which permits silica chip formation and the formation of silica dust on high speed paper rewind operations. The silica particles contribute to equipment wear, and high levels of silica dust are a health hazard for workers. In addition, since the temperature in the environment of a moving web is typically about 120xc2x0 F., when conventional colloidal silica compositions are spray-applied, they tend to dry during application and build up on the spray tip, eventually causing the tip to plug.
Various colloidal silica compositions for enhancing surface friction or imparting anti-slip properties to paper surfaces have been disclosed in U.S. Pat. Nos. 4,980,024, 3,860,431, 3,711,416 and 4,452,723. However there is still a need for a frictionizing composition that imparts long-term anti-slip properties to paper surfaces, which is easy to apply, and the residue of which is readily removable.
The present invention comprises an improved frictionizing composition for imparting anti-slip properties to the surface of paper on which it is applied. The frictionizing composition comprises an aqueous sol of colloidal silica, glycerin and at least one agent selected from the group consisting of N-methyl pyrrolidone (NMP), N,N-dimethyl acetoacetamide (DMAA), urea, sorbitol, fructose and dextrose. Surfaces coated with the frictionizing composition retain their anti-slip properties for an extended period of time. The frictionizing composition remains fluid, or retains the ability to flow, when exposed to drying conditions even for extended periods of time, and remains dispersible in water so that a residue of the composition can easily be removed with water.